Structural rules

A hierarchy type can define whether an entity type can act as a parent, a child, or both. It can also restrict which child entity types a parent can have and how many children of a particular type are allowed or required.

In Data Modeler, the Can be setting identifies an entity type as Parent only, Child only, or Parent & child.

If entity types are added to a hierarchy type, at least one must be able to act as a parent and at least one must be able to act as a child. A single Parent & child selection meets both requirements. If no entity types are added, all entity types are allowed.

For more information, see Create a hierarchy type and Edit a hierarchy type.

Validation during hierarchy operations

Advanced hierarchy management validates connections when a hierarchy is created or imported and when connections are added, moved, copied, or deleted.

A connection that violates a parent, child, or child-cardinality, isn't saved. Existing violations on nodes unaffected by the operation in the hierarchy doesn't prevent an otherwise valid connection from being added or changed.

Entity operations can also affect hierarchy structure. For example, merging entities from different parent locations can place the winning entity under multiple parents. If that placement violates a structural rule, Hub identifies the resulting violation.

For more information, see Effects of entity operations in Advanced hierarchy management.

Structural violations in Hub

The Hierarchy perspective displays a summary above the hierarchy when structural-rule violations are identified.

The summary shows:

• The number of identified issues.

• A message describing the affected entity and violated rule.

• A View action to view the hierarchy node that violated the rule.

Hub highlights the affected node in the hierarchy. Hover over the node to display Rule violated.

Select Rule violated next to the affected node to open the Resolve hierarchy issue dialog.

The issue summary includes violations detected when the hierarchy loads.

For more information, see Hierarchy perspective.

Validation messages

A violation message describes the affected entity and the structural rule that wasn't satisfied. Messages can identify the following conditions:

• An entity type that cannot act as a parent.

• An entity type that cannot act as a child.

• A child entity type that isn't permitted under a parent.

• Too many children of a particular entity type.

• A required child entity type that is missing.

• A node placement that results in an invalid parent structure.

For the complete message reference, see Structural validation messages for Advanced hierarchy management.